The boundary in question is a linear ditch, running roughly northwest to southeast across a gentle valley on the southern side of a U-shaped east-west depression, close to a small tributary that feeds into the King's River near the village of Ennisnag.

The ditch came to light in 2007, when road improvement works on the N9/N10 route between Kilcullen and Waterford prompted a programme of excavation across the area. The ditch itself carried no material that could be dated directly, but archaeologists working on the site used stratigraphic relationships, meaning the physical layering of deposits and how they cut across or underlie one another, to establish a rough chronology. Crucially, the lower fills of the ditch contained iron slag, the waste residue left behind by metalworking, and this pointed towards the middle Iron Age. That connection was reinforced by what else turned up in the same excavated area: a dedicated metalworking site and a ring-ditch, which is a circular ditched enclosure often associated with funerary or ritual use in prehistoric Ireland. Together, the three features suggest this quiet valley was once a place of some activity, where boundaries were drawn, metal was worked, and the dead, or at least the memory of them, were marked in the ground.